Air plants, what kind of plants are they?
There are a lot of different varieties of air plants, but their family name is Tillandsia. 

A Tillandsia is a plant that doesn't need any soil to survive, they grow on rocks an trees. Maybe now you would be thinking, are they parasite plants? But NO they aren't, they just like to stick around on other trees but they do not use their nutriciens. They call this kind of plants: Epifyt.
Air plants take their nutriciens from Light, Air and (rain)Water. 

Read here how to take care of air plants: Care Tips

Check here all Tillandsias

Decorations/gifts with airplants